The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Powertrain architectures comprise torque-generative devices, including internal combustion engines and electric machines, which transmit torque through a transmission device to an output. One exemplary transmission is a two-mode, compound-split, electromechanical transmission which utilizes an input member for receiving motive torque from a prime mover power source, for example an internal combustion engine, and an output member for delivering motive torque from the transmission to a vehicle driveline. Electric machines, operable as motors or generators, generate a torque input to the transmission, independently of a torque input from the internal combustion engine. The electric machines may transform vehicle kinetic energy, transmitted through the vehicle driveline, to electrical energy potential that is storable in the electrical energy storage device. A control system monitors various inputs from the vehicle and the operator and provides operational control of the powertrain system, including controlling transmission operating state and gear shifting, controlling the torque-generative devices, and regulating the electrical power interchange between the electrical energy storage device and the electric machines.
The exemplary electromechanical transmission is selectively operative in fixed gear and continuously variable operating state ranges through selective control of torque transfer clutch states, via a hydraulic circuit. The fixed gear operating state range occurs when rotational speed of the transmission output member is a fixed ratio of rotational speed of the input member from the engine, due to application and release states of one or more torque transfer clutches. The continuously variable operating state ranges occur when rotational speed of the transmission output member is variable based upon operating speeds of one or more of the electric machines. The electric machines are connected to the output shaft via application of one or more clutches. Selective clutch control is effected through a hydraulic circuit.